Large machine tools such as lathes, grinders and milling machines, and the like, must often be assembled where manufactured, then disassembled for transportation and reassembled at another site. In order to insure the most accurate reassembly and alignment of various parts of such devices, alignment fixtures, gibs, templates and other well-known arrangements have been utilized in industry.
It is common to provide in a base member, several close-tolerance alignment holes which receive removable alignment pins, along with less-accurate threaded openings which receive anchoring bolts for attachment of a mounted sub-unit. Preferred processing would be for the sub-unit to arrive at the assembly area with previously-machined mating close-tolerance holes, for final pinning with the base member. This technique works for small caps and parts, but large spacings of pin holes are frequently difficult to maintain in production machining procedures, especially when mating parts include many machining operations which inherently result in cumulative tolerance buildups which must be adjusted-out during final assembly. In these instances, assembled parts are drilled and reamed together for accommodating, for example, tapered pins. The pins may be removed and the assembly torndown and reassembled, using the tapered pins, with no loss in accuracy. Replacement units, however, will generally not match, and the entire alignment and pin-fixing technique must be performed by skilled assemblers, often at the field site.
Additionally, pin holes are often difficult to drill and ream during assembly, consuming time and generally contaminating the area and assembled devices with chips and debris.